A new U.S. $20 bill has been introduced. The redesigned banknote went into circulation on Thursday, but may take some time to show up everywhere. New technologies have made counterfeiting easier.

A splash of color has been added to the new U.S. $20 banknote, enlivening the drab green-and-black, traditionally used on U.S. banknotes. Although the visage of a somewhat-grim faced Andrew Jackson remains on the front of the bill, the portrait of the former president is set amidst light hues of blue and peach.

Michael Lambert, cash manager for the Federal Reserve, says the change is not for purely aesthetic reasons.

"Color in and of itself is not a security feature. But what it will do is raise the bar for counterfeiters," he said. "It makes the note more complex for them to have to reproduce this color, transitioning of color."

The new bills also retain some anti-counterfeiting measures introduced earlier, such as watermarks and security threads visible when the bill is held up to the light.

The $20 bill, says Mr. Lambert, is the favored note of counterfeiters.

Counterfeiting remains relatively rare, and most counterfeits are of poor quality. Nevertheless, Mr. Lambert says, the spread of home computers with inkjet printers has made casual counterfeiting easier.

"Prior to the last design series in 1996, the inkjet counterfeits contributed about one per cent of total counterfeits produced. By 2002, they were 40 per cent," he explained. "So what's happening is there are a lot of people who have personal computers at home, and they're capable of producing these with personal computers. So that has allowed more of the casual counterfeiter to reproduce U.S. currency."

Prior to 1996, U.S. banknotes had remained unchanged for some 70 or 80 years. But, Mr. Lambert says, redesigning the U.S. currency is becoming increasingly more frequent in order to keep pace with counterfeiting technology.

"We have to stay ahead of emerging technologies," he said. "And while technology changes and the sophistication is terrific, it also provides opportunity for potential counterfeiters. So, basically, the position we've taken, along with the Treasury Department, is to change the note regularly. It'll be an ongoing process, and we should expect to see design changes every seven to 10 years."

A new $50 dollar bill will be introduced next year, with a redesigned $100 dollar bill scheduled to be put in circulation in 2005. Changing $5 and $10 bills is also under consideration, but the lowest denominations $1 and $2 notes are expected to remain the same.